The permission is there, just not used....
PLEASE NOTE THAT IF YOU MAKE THESE CHANGES, SMFSHOP WILL FAIL TO UNINSTALL
open up
Sources/ManagePermissions.php
look for
'shop_trade' => false,
on the next line add
'shop_admin' => false,
open up
Themes/default/languages/ManagePermissions.english.php
look for
$txt['permissionname_shop_trade'] = 'Trade Centre';
on the next line add
$txt['permissionname_shop_admin'] = 'Shop Admin';